Gamerz Jackpot got updated every single day we had the site going, rats collectibles, hey come on I can't update if I don't get something new to add, sell something to replace. I needed the forums to give the spiders something *to* crawl.
The key word I should have emphasized there is
often. The frequency at which spiders will visit your site is based on traffic to the site (how it measures this varies, but typically its based on visitors from a search engine to your site).
A high-traffic site may be indexed hourly, a low-traffic site may be indexed fortnightly. It doesn't matter how often you update. Its how interested the search engines are in your site that determines spider activity.
And when a spider does come and index your site, it will index everything it can find. Images. Files. Webpages. Other. That's why a robots.txt file is recommended no matter how important the spiders are. The file tells them which parts of the site you want indexed and which parts are off-limits.